RAGE-AB Interactions in the Pathophysiology of Alzheimer's Disease

Abstract

RAGE is a cell surface molecule primarily identified for its capacity to bind advanced glycation end-products and amphoterin. Immunocytochemical studies demonstrated that in Alzheimer's Disease (AD) the expression of RAGE is elevated in neurons close to neuritic plaque beta-amyloid (AB) deposits and in the cells of AB containing vessels. Cross-linking of surface bound AB 1-40 to endothelial cells, yielded a band of 50 kDa identified as RAGE. Using the soluble extracellular domain of recombinant human RAGE, we found that AB binds to RAGE with a Kd = 57 ± 14 nM, a value close to those found for mouse brain endothelial cells and rat cortical neurons. The interaction of AB with RAGE in neuronal, endothelial, and RAGE-transfected COS-1 cells induced oxidative stress, as assessed by the TBARS and MTT assays. ELISA demonstrated a 2.5 times increase of RAGE in AD over control brains. Activated microglia also showed elevated expression of RAGE. In the BV-2 microglial cell line, RAGE bound AB in dose dependent manner with a Kd of 25 ± 9 nM. Soluble AB induced the migration of microglia along a concentration gradient, while immobilized AB arrested this migration. AB-RAGE interaction also activated NF-kB, resulting in neuronal up-regulation of macrophage-colony stimulating factor (M-CSF) which also induced microglial migration. Taken together, our data suggest that RAGE-AB interactions play an important role in the pathophysiology of Alzheimer's Disease.